Solid phase extraction has been used to extract analytes from water and other liquids to prepare them for analysis. For example, the technique has found success in monitoring drinking water by extraction of organics from the water followed by high pressure liquid chromatography separation and mass spectrometry (MS) detection to determine the identity and concentration of pollutants. Proteins and nucleic acid materials are frequently isolated from biological samples by passing them through a packed column and cartridge containing a solid phase where the molecules of interest are adsorbed. After the sample has passed through the column and the sample molecules have been adsorbed, a solvent is used to desorb the molecules of interest and form a concentrated solution.
It is particularly important to be able to purify and concentrate non-polynucleotide biomolecules such as polypeptides and polysaccharides, since these molecules are not amenable to the types of amplification techniques routinely used with nucleic acids. Many proteins and peptides are only expressed at extremely low levels, and in the presence of a vast excess of contaminating proteins and other cellular constituents. For this reason, it is often necessary to purify and concentrate a protein sample of interest prior to performing analytical techniques such as MS, SPR, NMR, X-ray crystallography and the like. These techniques typically only require a small volume of sample, but it must be presented at a sufficiently high concentration and interfering contaminants should be removed. Hence, there is a need for sample preparation methods that permit the manipulation and processing of small sample volumes with minimal sample loss.
Other desirable attributes of a sample preparation technology are the ability to purify and manipulate protein complexes. In many applications, it is also critical that the purified protein retain its native function.
Methods and reagents for performing solid phase extractions in open channels, such as open capillaries, are described in co-pending U.S. patent application Ser. No. 10/434,713. The instant disclosure follows up on that application, providing in some instances more specific and detailed teaching for performing open channel solid phase extractions. These methods, and the related devices and reagents, will be of particular interest to the life scientist, since they provide a powerful technology for purifying, concentrating and analyzing biomolecules and other analytes of interest. However, the methods, devices and reagents are not limited to use in the biological sciences, and can find wide application in a variety of preparative and analytical contexts.